Investigators said Crawford approached Jewish organizations last year looking for funding and people to help him with technology that could be used to surreptitiously deliver damaging and even lethal doses of radiation against those he considered enemies of Israel.

He and Feight assembled the mobile device, which was to be controlled remotely, but it was inoperable and nobody was hurt, authorities said.

‘‘Crawford has specifically identified Muslims and several other individuals/groups as targets,’’ investigator Geoffrey Kent said in a court affidavit.

According to the indictment, Crawford also traveled to North Carolina in October to solicit money for the weapon from a ranking member of the Ku Klux Klan, who informed the FBI. Crawford claimed to be a member.

The men appeared separately Wednesday in federal court in handcuffs and jail jumpsuits.

Magistrate Christian Hummel ordered them held until detention hearings Thursday. A lawyer was assigned to each man.

Neither said anything to the crowd that filled the courtroom gallery. They could face up to 15 years in prison. Messages left on answering machines at their homes were not returned Wednesday.

‘‘This case demonstrates how we must remain vigilant to detect and stop potential terrorists, who so often harbor hatred toward people they deem undesirable,’’ US Attorney Richard Hartunian said in a statement.

The damaging effects of the radiation would have appeared only days later, authorities said. The investigation by the FBI in Albany and police agencies began in April 2012 after authorities received information that Crawford had approached the Jewish organizations.

Crawford, an industrial mechanic for General Electric in Schenectady, knew Feight, an outside GE contractor with mechanical and engineering skills, through work, authorities said. Feight designed, built, and tested the remote control, which they planned to use to operate an industrial X-ray system mounted on a truck.

According to the indictment, the investigators had a confidential undercover source in place within weeks after learning of Crawford’s attempts to solicit money and later an undercover investigator introduced by the source.

They recorded meetings and conversations, and in December investigators got court authorization to tap Crawford’s phones, the indictment said.

Last June, the undercover investigator brought Crawford X-ray tubes to examine for possible use in the weapon, followed by their technical specifications a month later.

Crawford brought Feight to a November meeting in an Albany coffee shop with undercover investigators, and both said they were committed to building the device and named the group ‘‘the guild,’’ the indictment said.

Investigators gave Feight $1,000 to build the control device and showed the men pictures of industrial X-ray machines they said they could obtain.

They planned to provide him access to an actual X-ray system to assemble with the remote control on Tuesday.

According to court documents, the sealed indictment was filed the same day and both men were arrested.

GE spokesman Shaun Wiggins said they were informed Tuesday of Crawford’s arrest and he has been suspended from his job.

They have no information that any employees’ safety was compromised or the act he’s accused of occurred there.

BostonGlobe.com complimentary digital access has been provided to you, without a subscription, for free starting today and ending in 14 days. After the free trial period, your free BostonGlobe.com digital access will stop immediately unless you sign up for BostonGlobe.com digital subscription. Current print and digital subscribers are not eligible for the free trial.

Thanks & Welcome to Globe.com

You now have unlimited access for the next two weeks.

BostonGlobe.com complimentary digital access has been provided to you, without a subscription, for free starting today and ending in 14 days. After the free trial period, your free BostonGlobe.com digital access will stop immediately unless you sign up for BostonGlobe.com digital subscription. Current print and digital subscribers are not eligible for the free trial.